1. Field of the Invention
This invention relates to sprinkler systems and more specifically this invention relates to preaction telescopic automatic fire sprinkler systems in residential, commercial, and industrial buildings where the telescopic sprinkler assemblies are deployed repeatedly.
2. Background of the Invention
Automatic fire extinguisher sprinkler systems have become an integral part of modern residential, commercial, and industrial buildings. Automatic sprinkler systems also are used in agriculture and in several manufacturing processes. Commonly these systems include a network of pipes for distributing fluid (hereinafter designated as the "spray fluid") to a plurality of sprinkler heads. Often, the spray fluid is injected at high pressure in the pipe network only after a command therefor has been generated, either automatically, for instance, by a heat sensor for a fire-extinguishing system, or manually by an operator.
There are several applications where the sprinkler heads are not permanently installed in their spraying position but rather are installed in what are commonly referred to as "telescopic sprinkler systems". Some applications include anechoic enclosures, environmental chambers, and freezers.
In a telescopic sprinkler system, a sprinkler head is installed at a depending end of a conduit, or "piston". The first end of the piston is adapted to be slidably received by an "outer conduit" or cylinder. The outer conduit in turn is rigidly attached to the pipe network. When there is no high pressure in the fluid network, the piston is fully nested within the outer conduit. To deploy the sprinkler heads to their spraying positions, a high pressure fluid (for example either the spray fluid or compressed air) is injected into the network and the pistons are propelled outward at high speed until they strike a stop and suddenly come to rest.
Telescopic sprinkler systems also are utilized in a myriad of applications in addition to fire extinguishing. For instance, where a sprinkler system is used to provide water for agriculture or horticulture, the sprinkler heads are often installed underground so that they will not interfere with pedestrians, vehicles, or machinery above ground. Also, for esthetic reasons, some land owners prefer that the sprinkler heads not be visible when they are not in use. The same considerations apply to overhead sprinkler systems used for fire extinguishing. Often building users prefer that the sprinkler heads be recessed in the ceiling for esthetic reasons or because they would interfere with other equipment contained in the room. Moreover, designers of anechoic acoustical enclosures require that sprinkler heads be recessed in the ceiling so that they not generate unwanted reflections. Similarly, designers of enclosures shielded from radio frequency radiation require that the sprinkler heads be recessed so that they do not impart unwanted reflections.
High pressure telescopic sprinkler systems must be able to withstand repeated deployment. For instance, fire extinguisher systems are tested at regular intervals so as to ensure both that the piston pipes will deploy appropriately and that sprinkler heads are suitably positioned in case of a fire. This is accomplished by introducing high pressure air or water in the distribution system. This high pressure accelerates the piston downwardly and out of the outer conduit until it strikes a stop at very high velocity. High velocity piston/stop impacts cause the telescopic system to suffer considerable damage after only a small number of tests. Such slamming causes water to leak into the room. In extreme cases, either the stop, or a surface on the piston that is complementary to the stop, shears off causing the piston to shoot towards the floor of the facility. This leads to flooding and further damage in instances where the piston strikes an object. However, most damage is internal or otherwise undetected unless the telescopic system is taken apart after a test. Thus, tests of a telescopic sprinkling system provide inadequate assurance that the system will deploy properly in case of an actual fire.
Damage incurred by the telescopic system cannot be obviated by reducing the pressure of the fluid injected in the distribution network. Adequate operation of the sprayer heads require that the spray fluid be applied at high pressure. For such applications as fire extinguishing, a high volume of spray fluid must be sprayed as quickly as possible, requiring that the spray fluid be at high pressure. Finally, when the telescopic systems are not deployed frequently, there is considerable static friction impeding the deployment of the systems, and again high pressure is required to overcome this friction.
Examples of telescopic high pressure sprinkler systems are described in several United States patents. U.S. Pat. No. 3,194,316, issued Jul. 13, 1965, U.S. Pat. No. 3,847,392, issued Nov. 12, 1974, U.S. Pat. No. 3,675,952, issued Jul. 11, 1972, U.S. Pat. No. 4,091,872, issued Mar. 30, 1978, and U.S. Pat No. 5,160,174, issued Nov. 3, 1992, teach methods for adjusting the length of a telescopic sprinkler system when it is first installed but make no provision for regulating the speed of deployment of such systems. U.S. Pat No. 3,263,929, issued Aug. 2, 1966, is an overhead sprinkler system for watering lawns. It incorporates an air chamber complete with an evacuation port. The air chamber is used to selectively actuate a specific sprinkler, but again no provision is made for regulating the speed of deployment of the telescopic sprinkler.
A need exists in the art to provide telescopic sprinkler systems for fire extinguishing and other applications wherein the velocity of the piston/stop impact is regulated so as to prevent damage to the telescopic assembly during testing or in actual fire-suppression scenarios.